The present invention relates to a photocurable diallyl phthalate resin composition usable for producing printed circuit boards and a process for producing a printed circuit board using said resin composition as an ultraviolet (UV) exposure developing type solder resist having resistance to peeling from a copper foil.
UV exposure developing type solder resists for printed circuit boards are disclosed, for example, in Japanese Patent Examined Publication Nos. 51-40451 and 52-30969, Japanese Patent Unexamined Publication Nos. 60-208377, 62-4390, and 62-253613, etc. These solder resists are mainly used in a subtractive process. On the other hand, plating resistant solder resists used in a so-called partly additive process are required to have quite different properties from those used in the subtractive process. Such solder resists are disclosed, for example, in Japanese Patent Unexamined Publication No. 58-147416.
But when a UV exposure developing type resist disclosed, for example, in Japanese Patent Examined Publication No. 52-30969 was used in the partly additive process, the resist had no resistance to peeling of the resist from a copper foil coated thereunder. On the other hand, when the solder resist disclosed in Japanese Patent Unexamined Publication No. 58-147416 was used, resistance to plating was good, but since it was not a UV exposure developing type, there was a problem in that highly precise patterns were not able to be formed.
In order to solve such problems, Japanese Patent Unexamined Publication No. 62-265321 discloses a resist composition usable for printed circuit boards comprising a prepolymer of diallyl phthalate, a polyfunctional unsaturated compound, a photopolymerization initiator, an epoxy resin, and a curing agent for the epoxy resin. Said composition may contain a filler, but the working examples disclosed in said patent publication contain no filler. The sholder resist obtained from said composition is good in resistance to alkaline plating, has a high degree of resolution and good workability, but poor in prevention of an effect of UV light reaching to a back side of a substrate coated with a resist on both sides when exposed to UV light (hereinafter referred to as "prevention of back side undesirable curing") and in resistance to release of substances from a resist in an electroless plating bath (hereinafter referred to as "resistance to release from a resist"), and inferior in heat resistance.